1. Field of the Invention
The invention relates to a non-trackbound vehicle such as passenger cars and trucks for street traffic and, more particularly, to a non-trackbound vehicle including at least one wheel coupled for propulsion with an electronic motor (12, 16) supplied with a controlled current by an electronic energy distributor.
2. Description of the Prior Art
The invention relates primarily to passenger cars and trucks for street traffic. Generally, such vehicles are equipped with internal combustion engines for supplying the necessary driving energy. The number of vehicles powered by battery-supplied electric motors is infinitesimally small.
In the case of either an internal combustion engine, the characteristics of the torque, which are specific for the engine, makes the use of either a manual or automatic transmission necessary depending on the rmp, in order to produce the torque or driving power required for the driving behavior available at the driving wheels.
In the case of vehicles driven by an electric motor, there is basically no need for a transmission in the drive train of the vehicle, since electric motors produce a relatively high torque over a wide range of rpm, so that gear switching is not applicable.
A non-trackbound vehicle of the above-mentioned type has already been proposed. For this prior art vehicle, current is produced by an internal combustion engine/generator (ICEGU) unit, which is then supplied over an energy distributor/power electronics system to the electric motors coupled with the vehicle. For this purpose, the current is supplied to the electric motors as a function of a driving signal, serving as a desired value signal, taking into consideration the operating behavior of the internal combustion engine.
Such a driving mechanism results in several advantages, which either cannot be achieved or can only be achieved at considerable expense by a driving mechanism having a conventional internal combustion engine. For example, slippage of the wheels can be controlled by each driving mechanisms without great expense. In the case of a braking process, the electric motors, coupled with the wheels, can work as generators. Furthermore, the electric energy gained can be used, for example, for heating purposes or the like.
In such a vehicle, with a generator coupled to an internal combustion engine and wheels driven by way of electric motors, is used, for example, in city traffic, the operation of rpm of the internal combustion engine is varied to correspond with the power required. However, frequent changes in the rpm of the internal combustion engine result in an impairment of the efficiency of the internal combustion engine; after all, a frequent change in the rpm is naturally associated with a frequent operation in a region of the family of characteristic curves of the engine in which parameters, such as the minimum fuel consumption for a given power, the least exhaust emission, the least development of noise and the like, have a value, are not optimal.
German Patent application DE 37 25 620 A1 discloses a driving and braking concept for motor vehicles having an internal combustion engine that drives an electric generator. The internal combustion engine is constructed as a pivoting piston engine. The current, produced by the generator, is supplied by an energy distributor, constructed as a power electronics system, in accordance with a control signal generated in dependence on a driving signal, to electric driving motors, which are coupled in each case with one driving wheel or the current is optionally partially stored on an interim basis in a flywheel storage system, which contains an electric machine that can be operated alternately as a motor or generator. When the vehicle is being braked, the electric driving motors can be switched by an electronic control unit, which affects the driving operation, into the generator mode so that at least a portion of the braking energy, after conversion into electrical energy, can be taken up by the flywheel storage system. If required, the control unit can also supply energy from the flywheel storage system via the power electronics system to the driving motors. In this system, the pivoting piston engine is operated at a constant rmp, since the generator, which is rigidly coupled to the pivoting piston engine, generates an alternating current with a constant load frequency at all times. The rpm of the driving wheels is adjusted to the desired value by a control unit using an appropriate corresponding frequency conversion so that there exists a quasi infinitely variable electric transmission between the pivoting piston engine and the driving wheels. A component of the control unit is a "characteristics-programmed" microprocessor which, in the event that the vehicle is braked, generates the required braking force on a conventional wheel braking system and distributes it to the electric driving motors operating in the generator mode. In this connection, the programming of the characteristic refers to characteristics data external to the operation of the internal combustion engine (such as the state of charge of the flywheel storage system, as well as the frequency of the alternating current supplied via the frequency converter and the driving speed and accelerator pedal position). Controlling the internal combustion engine for adapting it to different output requirements based upon characteristic data of the internal combustion engine itself (particularly the rpm/torque characteristics as a function of the position of the throttle valve, advance angle setting, consumption, amount and composition of exhaust, noise emission, unit wear) is not taken into consideration. In this respect, a driving operation, which is optimized with respect to the internal combustion engine, is not ensured for this vehicle for all driving situations.
A non-trackbound vehicle such as passenger cars and trucks for street traffic and, more particularly, to a non-trackbound vehicle including at least one wheel coupled for propulsion with an electronic motor (12, 16) supplied with a controlled current by an electronic energy distributor is known from European Patent Reference No. EP-A-437266.